I went to my local store yesterday and found this offer at the front of the store.
They were reduced from £2 due to the pet event, to £1 then to 50p.
I believe this is to clear old stock, however the best before date is October 2011 on the packs i purchased. They are available in the meat or fish variety. I don't know how long they will be in store for, as they were flying off the shelves in the 20mins that i was in there.
Wilkinsons sell the individual cans for 45p!